Passive Leg Raise: Search Method and Summary of the Studies

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Table of Contents

Introduction
Search Method
Summary of the Studies
Conclusion
References

Introduction

Patients diagnosed with hypotension usually have a low level of water in the body. To solve this problem, it is typical to resort to intravenous fluid resuscitation (Kyriakides et al., 1994). However, it is often unclear when and how much additional fluid is necessary for maintaining cardiac functions. Passive leg raise (PLR) is a maneuver that makes it possible to shift the patients blood from the lower body to the top, which simulates rapid fluid loading thereby increasing stroke volume and improving blood pressure outcomes (Ohashi et al., 1997). This test should be implemented in clinical settings since it allows avoiding hypotension by predicting fluid responsiveness in patients (Teboul, Monnet, & Richard, 2005).

Search Method

To investigate the existing studies on the topic, Google Scholar, National Guideline Clearinghouse, Ovid, CINANL, and Medline were used as the major databases since they contain the biggest number of articles satisfying my search parameters. The keywords I used included: passive leg raise, hypotension, fluid resuscitation, fluid responsiveness, reflex control, and the Trendelenburg position. The criteria for inclusion were the relevance of the topic to the given research, the English language used in the study, and the time period of publication between 1990 and 2005. Articles published earlier than in 1990 and in other languages were excluded from the search. Although the number of results partially meeting the specified parameters exceeded 10.000, 6 studies were selected from the list since they could best support the present research.

Summary of the Studies

Bridges and Jarquin-Valdivia (2005).conducted a review of literature on the use of Trendelenburg position as a way for resuscitation of patients suffering from hypotension. They searched Pubmed online, critical care textbooks, cited bibliographies, and Advanced Cardiac Life Support guidelines. The authors claimed that literature on the topic was scare and unreliable and concluded that the position was not good for hypotensive patients, which speaks in favor of PLR. The major strengths of the study is its extensive coverage (articles from 1964 to 2004). The search was limited by the language of publications and the restricted number of key words.

Kyriakides et al. (1994) evaluated the effects of passive leg raise on cardiovascular performance in 31 patients of 51 ± 10. They obtained two M-mode echocardiographic and continuous wave Doppler studies of aortic flow, the first of which was before and the secondafter the intervention. The preload increased, and it was concluded that PLR improved cardiac performance. The major strength of the study is that is supported by clinical trials while the limitation is a small sample.

Mancia et al. (1991) studied the baroreceptor ability of patients and found out that its fall brings about blood pressure changes. They concluded that cardiopulmonary receptor modulation of vascular resistance was impaired by aging, which accounted for some hemodynamic abnormalities in the advanced age. The strength of the research is that it supports the necessity of intervention in the elderly. Its limitation is the absence of recommendations, which intervention is more suitable.

Pinsky and Payen (2005) investigated hemodynamic monitoring involving therapeutic trials of preload responsiveness. They assessed the effectiveness of several functional measures (indicated by other studies), including change monitoring in central venous pressure during spontaneous inspiration, systolic pressure, variations in arterial pulse pressure, and aortic flow variation as a response to PLR or vena caval collapse during positive pressure ventilation. The authors concluded that these measures could improve blood pressure outcomes. The strength of the study is the comparison of several methods while its limitation is the absence of statistical evidence.

Rebain, Baxter, and McDonough (2002) conducted a systematic review of papers from six computerized bibliographic databases on PLR to assess the procedure, its outcome, and clinical significance. The authors found out that the procedure had no set protocol. Neither was there any consensus of result interpretation. Moreover, it was unclear if a positive or negative outcome of the test was of higher diagnostic value. The strength of the study is that it is supported by extensive evidence. However, it is limited by the aspect of PLR application (by its ability to traction the sciatic nerve).

Rex et al. (2004) conducted a research involving 14 patients after coronary artery bypass grafting, who received mechanical ventilation in pressure-controlled mode. They measured stroke volume index, cardiac index, and intrathoracic blood volume index before and after implementing the Trendelenburg position. They discovered that stroke volume variation (SVV) decreased significantly whereas other indicators increased. It was concluded that the haemodynamic effects of volume loading could be assessed by measuring SVV. The strength of the research is the use of several indicators to evaluate the intervention. Its limitation is a small sample. The result obtained by this study will be compared with the ones of PLR implementation to compare the effectiveness of the interventions.

Conclusion

The majority of the mentioned studies are retrospective and did not involve any intervention. This implies that there is a need in empirical evidence to support the effectiveness of PLR. The strength of the research at hand is its experimental design. Its limitation is that the sample will be restricted to patients of one hospital. Internal validity will be ensured by the research design and the selected variables (blood pressure variations during the intervention). This will guarantee that the change in the dependent variable (blood pressure) will be brought about exclusively by the independent variable (PLR) excluding the effect of extraneous variables. External validity will be ensured by randomization, single intervention, pretesting, and experimental setting. This way, it will be possible to generalize the results and apply them to different clinical settings.

References

Bridges, N., & Jarquin-Valdivia, A. A. (2005). Use of the Trendelenburg position as the resuscitation position: To T or not to T? American Journal of Critical Care, 14(5), 364-368.

Kyriakides, Z. S., Koukoulas, A., Paraskevaidis, I. A., Chrysos, D., Tsiapras, D., Galiotos, C., & Kremastinos, D. T. (1994). Does passive leg raising increase cardiac performance? A study using Doppler echocardiography. International Journal of Cardiology, 44(3), 288-293.

Mancia, G., Cleroux, J., Daffonchio, A., Ferrari, A. U., Giannattasio, C., & Grassi, G. (1991). Reflex control of circulation in the elderly. Cardiovascular Drugs and Therapy, 4(1), 1223-1228.

Ohashi, M., Sato, K., Suzuki, S., Kinoshita, M., Miyagawa, K., Kojima, M., & Dohi, Y. (1997). Doppler echocardiographic evaluation of latent pulmonary hypertension by passive leg raising. Coronary Artery Disease, 8(10), 651-656.

Pinsky, M. R., & Payen, D. (2005). Functional hemodynamic monitoring. Critical Care, 9(6), 566-578.

Rebain, R., Baxter, G. D., & McDonough, S. (2002). A systematic review of the passive straight leg raising test as a diagnostic aid for low back pain (1989 to 2000). Spine, 27(17), E388-E395.

Rex, S., Brose, S., Metzelder, S., Hüneke, R., Schälte, G., Autschbach, R.,& Buhre, W. (2004). Prediction of fluid responsiveness in patients during cardiac surgery. British Journal of Anaesthesia, 93(6), 782-788.

Teboul, J. L., Monnet, X., & Richard, C. (2005). Arterial pulse pressure variation during positive pressure ventilation and passive leg raising. Functional Hemodynamic Monitoring, 3(2), 331-343.

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Passive Leg Raise: Search Method and Summary of the Studies

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